PROJECT SUMMARY The long-term goal of this investigation is to elucidate the mechanisms by which HIV-1 accessory protein Vpr alters host defense pathway to enhance HIV-1 persistent infection and pathogenesis. This investigation is proposed based on five key findings we made recently. (1) HIV-1 infection induces efficient production of type I interferons (IFN-I) by activating pDC, which fails to control HIV-1 infection but rather contributes to HIV-1 diseases. (2) HIV accessory protein Vpr plays an important role to counteract the effect of IFN-I to promote HIV-1 infection. (3) TET methylcytosine dioxygenases are monoubiquitylated by the VprBP-DDB1-CUL4-ROC1 (CRL4VprBP) E3 ligase which promotes TET binding to chromatin. (4) TET2 is recruited by sequence-specific transcription factors (TFs) to and activates the expression of specific target genes, including a subset of interferon (IFN)-stimulated genes (ISGs) and viral-defense genes. (5) Vpr interacts with both VprBP and TET and reprograms CRL4VprBP ligase to catalyze polyubiquitylation of TET2, resulting in TET2 degradation and inhibition of TET2-mediated induction of ISGs, including three HIV restriction factors. We propose that there exists an IFN-JAK-STAT-TET-ISG pathway that modulates IFN signaling and the expression of a subset of ISGs. The Vpr-mediated degradation of TET disrupts this pathway and counteracts the anti-HIV effect of IFN in human cells but not the IFN induction pathway, thereby promoting HIV-1 infection and persistence in the presence of IFN-I, which contributes to HIV-induced inflammation and pathogenesis. We propose four specific aims to test this hypothesis. Aim 1 will determine the function and mechanism Vpr- mediated TET degradation. Aim 2 is to determine the mechanism of the IFN-JAK-STAT-TET-ISG pathway. Aim 3 will study how Vpr and the IFN-STAT-TET pathway modulate HIV-1 infection and persistence in vivo, including the establishment and rebound of HIV-1 reservoir during cART. Aim 4 will investigate how Vpr disrupts the IFN-TET pathway to contribute to HIV-induced inflammation and T cell depletion/impairment. Combining the expertise of the two PIs in HIV virology and immunology, ubiquitin pathway and TET-mediated epigenetic control and motivated by a series of recent key findings, this investigation will establish the IFN- JAK-STAT-TET-ISG pathway in HIV-1 target cells and determine how Vpr disrupts this pathway to lead to persistent HIV infection and the HIV-associated inflammation. This investigation will also gain insights into DNA de/methylation as a mechanism in dynamic gene regulation and immune response, identify novel viral and host targets for developing HIV-1 ?cure? treatments, and establish a paradigm on how this novel pathway is involved in the general anti-viral mechanism against other human viruses. 1